Aspects of this disclosure relate generally to telecommunications, and more particularly to signals used for mobility in wireless communication systems.
Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power). Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, and single-carrier frequency division multiple access (SC-FDMA) systems.
These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. For example, 5G new radio (NR) communications technology is envisaged to expand and support diverse usage scenarios and applications with respect to current mobile network generations. In an aspect, 5G communications technology includes enhanced mobile broadband addressing human-centric use cases for access to multimedia content, services and data; ultra-reliable-low latency communications (URLLC) with strict requirements, especially in terms of latency and reliability; and massive machine type communications for a very large number of connected devices and typically transmitting a relatively low volume of non-delay-sensitive information. As the demand for mobile broadband access continues to increase, however, there exists a need for further improvements in 5G communications technology and beyond. Preferably, these improvements should be applicable to other multi-access technologies and the telecommunication standards that employ these technologies.
Known communications systems such as long term evolution (LTE) and high-speed packet access (HSPA) may use downlink based mobility procedures to change a serving cell of a UE. In a downlink based mobility procedure, the UE may measure downlink signals from a serving cell and/or neighbor cells. The UE and/or the network may then determine whether the UE should change cells based on the quality of the downlink signals.
It is envisaged that 5G NR will, in some cases, allow a user equipment (UE) to transition between connectivity states for radio resource control (RRC). An RRC-Idle state may be an initial state where the UE has no context in a radio access network (RAN) and is not assigned any air interface resources. An RRC-Common state may be used when a UE has little traffic. In the RRC-Common state, the UE may have a context in the radio access network but no assigned air interface resources. An RRC-Dedicated state may be used when a UE has large amounts of traffic (e.g., active applications or streams). In the RRC-Dedicated state, a UE may have a context in the radio access network and be assigned air interface resources.
In some cases, a downlink based mobility procedure may not be ideal for a UE. In an uplink based mobility procedure, one or more base station may measure a signal transmitted by the UE. The network may then determine whether to change the serving cell for the UE. Due to the various connectivity states in 5G NR, there is a need for the UE to be able to obtain information to complete either a downlink, uplink, or hybrid mobility procedure in various connectivity states.